No release in over 3 years
Low commit activity in last 3 years
There's a lot of open issues
== A port of the Java {Typesafe Config}[] library to Ruby


~> 2.14
 Project Readme


Gem Version Build Status

This is a port of the Typesafe Config library to Ruby.

The library provides Ruby support for the HOCON configuration file format.

At present, it supports parsing and modification of existing HOCON/JSON files via the ConfigFactory class and the ConfigValueFactory class, and rendering parsed config objects back to a String (see examples below). It also supports the parsing and modification of HOCON/JSON files via ConfigDocumentFactory.

Note: While the project is production ready, since not all features in the Typesafe library are supported, you may still run into some issues. If you find a problem, feel free to open a github issue.

The implementation is intended to be as close to a line-for-line port as the two languages allow, in hopes of making it fairly easy to port over new changesets from the Java code base over time.


For best results, if you find an issue with this library, please open an issue on our Jira issue tracker. Issues filed there tend to be more visible to the current maintainers than issues on the Github issue tracker.

Basic Usage

gem install hocon

To use the simple API, for reading config values:

require 'hocon'

conf = Hocon.load("myapp.conf")
puts "Here's a setting: #{conf["foo"]["bar"]["baz"]}"

By default, the simple API will determine the configuration file syntax/format based on the filename extension of the file; .conf will be interpreted as HOCON, .json will be interpreted as strict JSON, and any other extension will cause an error to be raised since the syntax is unknown. If you'd like to use a different file extension, you manually specify the syntax, like this:

require 'hocon'
require 'hocon/config_syntax'

conf = Hocon.load("myapp.blah", {:syntax => Hocon::ConfigSyntax::HOCON})

Supported values for :syntax are: JSON, CONF, and HOCON. (CONF and HOCON are aliases, and both map to the underlying HOCON syntax.)

To use the ConfigDocument API, if you need both read/write capability for modifying settings in a config file, or if you want to retain access to things like comments and line numbers:

require 'hocon/parser/config_document_factory'
require 'hocon/config_value_factory'

# The below 4 variables will all be ConfigDocument instances
doc = Hocon::Parser::ConfigDocumentFactory.parse_file("myapp.conf")
doc2 = doc.set_value("a.b", "[1, 2, 3, 4, 5]")
doc3 = doc.remove_value("a")
doc4 = doc.set_config_value("a.b", Hocon::ConfigValueFactory.from_any_ref([1, 2, 3, 4, 5]))

doc_has_value = doc.has_value?("a") # returns boolean
orig_doc_text = doc.render # returns string

Note that a ConfigDocument is used primarily for simple configuration manipulation while preserving whitespace and comments. As such, it is not powerful as the regular Config API, and will not resolve substitutions.

CLI Tool

The hocon gem comes bundles with a hocon command line tool which can be used to get and set values from hocon files

Usage: hocon [options] {get,set,unset} PATH [VALUE]

Example usages:
  hocon -i settings.conf -o new_settings.conf set some.nested.value 42
  hocon -f settings.conf set some.nested.value 42
  cat settings.conf | hocon get some.nested.value

  get PATH - Returns the value at the given path
  set PATH VALUE - Sets or adds the given value at the given path
  unset PATH - Removes the value at the given path

    -i, --in-file HOCON_FILE         HOCON file to read/modify. If omitted, STDIN assumed
    -o, --out-file HOCON_FILE        File to be written to. If omitted, STDOUT assumed
    -f, --file HOCON_FILE            File to read/write to. Equivalent to setting -i/-o to the same file
    -j, --json                       Output values from the 'get' subcommand in json format
    -h, --help                       Show this message
    -v, --version                    Show version

CLI Examples

Basic Usage

$ cat settings.conf
  foo: bar

$ hocon -i settings.conf get foo

$ hocon -i settings.conf set foo baz

$ cat settings.conf
  foo: baz

# Write to a different file
$ hocon -i settings.conf -o new_settings.conf set some.nested.value 42
$ cat new_settings.conf
  foo: bar
  some: {
    nested: {
      value: 42


# Write back to the same file
$ hocon -f settings.conf set some.nested.value 42
$ cat settings.conf
  foo: bar
  some: {
    nested: {
      value: 42


Complex Values

If you give set a properly formatted hocon dictionary or array, it will try to accept it

$ hocon -i settings.conf set foo "{one: [1, 2, 3], two: {hello: world}}"
  foo: {one: [1, 2, 3], two: {hello: world}}


If --in-file or --out-file aren't specified, STDIN and STDOUT are used for the missing options. Therefore it's possible to chain hocon calls

$ cat settings.conf
  foo: bar

$ cat settings.conf | hocon set foo 42 | hocon set one.two three
  foo: 42
  one: {
    two: three

JSON Output

Calls to the get subcommand will return the data in HOCON format by default, but setting the -j/--json flag will cause it to return a valid JSON object

$ cat settings.conf
foo: {
  bar: {
    baz: 42

$ hocon -i settings.conf get foo --json
    "bar": {
        "baz": 42


bundle install --path .bundle
bundle exec rspec spec

Unsupported Features

This supports many of the same things as the Java library, but there are some notable exceptions. Unsupported features include:

  • Non file includes
  • Loading resources from the class path or URLs
  • Properties files
  • Parsing anything other than files and strings
  • Duration and size settings
  • Java system properties